Nonlinear Behavior Research Articles

Mechanical testing and numerical simulation of intelligent terminal structure of rockbolt used as a deformable support and for safety monitoring in rock engineering

The nonlinear mechanical behavior perception and deformation control of engineering rock masses are crucial technical challenges in the fields of underground engineering support and safety monitoring. An intelligent terminal structure (ITS) of rockbolts was designed for deformable support systems and safety monitoring in rock engineering applications. It is a type of device installed at the end of a traditional bolt. The ITS comprises two key components: a memory tooth and a yielding ring. This study introduces the design principle of an ITS in deformable rockbolt support systems. It proposes design parameters for the ITS in relation to the deformations encountered by engineering rockbolts. Tests were conducted to measure the ultimate bearing capacity and deformation of the ITS under pull-out conditions. The results demonstrate that the ITS of rockbolt undergoes deformation in the form of elongation as opposed to conventional bolts. Furthermore, finite element numerical simulations were conducted to investigate the mechanism of interaction between the memory tooth and yielding ring of the ITS. The numerical simulation results are consistent with the experimental results. The load capacity of the yielding ring exceeded that of the memory tooth. The field test results indicate that the dilatation of the surrounding rock mass causes ITS deformation in the diversion tunnel. The axial stress load exerted on the rockbolt is transferred to the ITS, leading to memory tooth breakage and compression deformation of the yielding ring. This mechanism allows the load and deformation of the surrounding rock mass to be reflected. The ITS not only serves as a deformable support system but also plays a significant role in monitoring the stress and deformation of the rock mass.

Shake table test on support uplift force of long-span cable-stayed bridge under longitudinal ground motions

Since the excessive seismic support uplift force may cause the support failure of long-span cable-stayed bridges, this study focused on the support uplift force at the auxiliary pier for a double-tower cable-stayed bridge with a main span of 1088 m. A shake table test was designed and performed based on the 1/35-scale test model scaled from the prototype bridge. Details of the test model, including the scale factor, structural member configurations, boundary conditions, and the numerical validation were briefly presented. The test results show that although only the longitudinal ground motion was applied, significant seismic support uplift and compression forces would be generated in the bearings at the auxiliary pier, resulting in the bearing uplift. The vertical vibration of the deck contributed by the first vibration mode of the test model was one of the main causes of the bearing uplift, but no rigid-like pounding effect occurred due to the vertical nonlinear mechanical behaviour of the bearing. Furthermore, the effect of the bearing uplift on the main seismic responses of the test model was negligible.

Fractional-order view analysis of Fisher’s and foam drainage equations within Aboodh transform

PurposeThe purpose of this study is to solve two unique but difficult partial differential equations: the foam drainage equation and the nonlinear time-fractional fisher’s equation. Through our methods, we aim to provide accurate solutions and gain a deeper understanding of the intricate behaviors exhibited by these systems.Design/methodology/approachIn this study, we use a dual technique that combines the Aboodh residual power series method and the Aboodh transform iteration method, both of which are combined with the Caputo operator.FindingsWe develop exact and efficient solutions by merging these unique methodologies. Our results, presented through illustrative figures and data, demonstrate the efficacy and versatility of the Aboodh methods in tackling such complex mathematical models.Originality/valueOwing to their fractional derivatives and nonlinear behavior, these equations are crucial in modeling complex processes and confront analytical complications in various scientific and engineering contexts.

An inelastic beam-like model for nonlinear dynamic analyses of multi-storey buildings

This paper presents an equivalent non-uniform inelastic beam-like model for the evaluation of the nonlinear behaviour of multi-storey buildings subjected to earthquake loadings. The proposed beam can be used to model buildings with non-uniform mass and stiffness distribution. The model is characterised by a number of degrees of freedom corresponding to the number of floors of the building and is conceived to predict its nonlinear dynamic response after a proper calibration based on the results of pushover analyses performed on a nonlinear FEM model. In spite of its simplicity, the proposed equivalent model provides, with a very low computational effort, an accurate representation of the nonlinear dynamic behaviour of the building comparable to that obtained through the more demanding nonlinear 3D FEM models. The effectiveness of the proposed simplified modelling approach is here validated by means of nonlinear dynamic analyses firstly performed on a benchmark known in the literature as SAC9 building, modelled as a plane steel frame structure and secondly on a three-dimensional reinforced concrete structure, designed according to old standard structural design rules. The very good agreement with the results obtained through accurate 3D FEM frame modelling, for different earthquake loadings, on the considered benchmarks provides a first validation of the proposed inelastic equivalent beam-like model and suggests its potential use for the seismic assessment of building structures. The low computational cost related to the beam-like model could be particularly advantageous for all the seismic vulnerability approaches requiring several nonlinear dynamic analyses, as those related to large scale applications, or those expressed in terms of probability of failure generally expressed in terms of fragility curves.

Effect of temperature on ferroelastic and creep behavior of LaCoO3

The study investigates the time-dependent deformation of LaCoO3 under constant uniaxial compressive stresses at various temperatures ranging from room temperature to 880 °C. Through the acquisition of stress-strain curves at different temperatures, it has been observed that LaCoO3 exhibits non-linear ferroelastic behavior. The stiffness of LaCoO3 increases with temperature, up to 600 °C, after which it starts to decrease at higher temperatures. Furthermore, negative creep occurs at lower temperatures, whereas positive creep is observed at temperatures exceeding 600 °C. This can be attributed to transitioning from a ferroelastic creep at low temperatures to a combination of ferroelastic and high-temperature conventional creep at temperatures above 600 °C. The magnitude of both negative and positive creep is proportional to the temperature. The structural stability of LaCoO3 under creep loading at all temperatures has been assessed by comparing pre-test and post-test X-ray diffraction analyses, which showed the texture formation after testing.

Remote sensing image information extraction based on Compensated Fuzzy Neural Network and big data analytics

Medical imaging AI systems and big data analytics have attracted much attention from researchers of industry and academia. The application of medical imaging AI systems and big data analytics play an important role in the technology of content based remote sensing (CBRS) development. Environmental data, information, and analysis have been produced promptly using remote sensing (RS). The method for creating a useful digital map from an image data set is called image information extraction. Image information extraction depends on target recognition (shape and color). For low-level image attributes like texture, Classifier-based Retrieval(CR) techniques are ineffective since they categorize the input images and only return images from the determined classes of RS. The issues mentioned earlier cannot be handled by the existing expertise based on a keyword/metadata remote sensing data service model. To get over these restrictions, Fuzzy Class Membership-based Image Extraction (FCMIE), a technology developed for Content-Based Remote Sensing (CBRS), is suggested. The compensation fuzzy neural network (CFNN) is used to calculate the category label and fuzzy category membership of the query image. Use a basic and balanced weighted distance metric. Feature information extraction (FIE) enhances remote sensing image processing and autonomous information retrieval of visual content based on time-frequency meaning, such as color, texture and shape attributes of images. Hierarchical nested structure and cyclic similarity measure produce faster queries when searching. The experiment’s findings indicate that applying the proposed model can have favorable outcomes for assessment measures, including Ratio of Coverage, average means precision, recall, and efficiency retrieval that are attained more effectively than the existing CR model. In the areas of feature tracking, climate forecasting, background noise reduction, and simulating nonlinear functional behaviors, CFNN has a wide range of RS applications. The proposed method CFNN-FCMIE achieves a minimum range of 4–5% for all three feature vectors, sample mean and comparison precision-recall ratio, which gives better results than the existing classifier-based retrieval model. This work provides an important reference for medical imaging artificial intelligence system and big data analysis.

Analysis of bifurcation and chaotic behavior of the micro piezoelectric pipe-line robot drive system with stick - slip mechanism

Pipeline robots using the conventional driving mode have encountered a bottleneck in miniaturization. To address this problem, a micro piezoelectric pipeline robot based on the inertia stick-slip driving principle is proposed in this paper. The robot is well suited to the inspection needs of micro pipes. However, undesirable design parameters found during the structural optimization phase can lead to unstable operation and reduced load capacity of the robot, and can even cause the drive system to stop with chaotic behavior. Therefore, the nonlinear dynamics model of the four degree of freedom discrete system of the pipeline robot is established. The Runge-Kutta method is used to solve the dynamic response of each nonlinear subsystem. The nonlinear dynamical behavior of the system is analyzed through the bifurcation diagram, time domain diagram, phase diagram, Poincaré map and power spectrum diagram of each subsystem response. The stable operation intervals of the machine and electrical parameters in the drive system are given, and the conditions for the occurrence of chaotic behavior are determined. This research can be applied to most of the drive systems consisting of piezoelectric stacks and flexure hinges. It helps to determine and optimize the structural parameters of the piezoelectric actuator, thus avoiding chaotic behavior and ensuring that the actuator maintains good operational performance.

Role of SiO2 in tailoring stability and nonlinear optical behaviour of gold nanoparticles in glass

In the present work, a new approach is introduced to mitigate the loss of gold nanoparticles while preparing the glass through the traditional melt-quench technique. The role of refractory material i.e. SiO2 in loss reduction is studied by comparing the results obtained for bismuth borate (40Bi2O3:60B2O3) and borosilicate (40Bi2O3:40B2O3:20SiO2) glasses containing gold nanoparticles of different sizes (10 nm, 40 nm and 100 nm). The particle density and thermal stability obtained from FESEM and DTA, respectively, increase considerably with the presence of SiO2 as one of the components of glass composition. The nonlinear optical behaviour of both systems in non-resonant regions has been obtained using the Z-scan technique. In addition, the suitability of the prepared glasses for optical limiting and switching applications has been analysed.

Numerical Simulation of T Joints Constructed from Hollow Steel Sections

Welded structural hollow sections are becoming increasingly used in contemporary civil engineering buildings. More specific design techniques are needed for connections in steel structures with welded structural hollow sections than for traditional connections made with gusset plates. At the connecting site, stress and local deformations show very complex, non-linear behaviors. The application of non-linear numerical analyses to determine the ultimate bearing capacity of “T” connections was demonstrated in this study. A non-linear material model was used in the analysis. In order to validate the applicable steel modeling method, a comparative study between experimentally obtained results and analytically and numerically computed ultimate bearing capacities was carried out. The comparison showed good agreement between the numerical and experimental results and pointed out the highly conservative design of such joints was obtained using the analytical solution.

Dynamic Behavior and Permanent Indentation in S2-Glass Woven Fabric Reinforced Polymer Composites under Impact: Experimentation and High-Fidelity Modeling

This paper studies the behavior of S2-glass woven fabric reinforced polymer composite under low-velocity impact at 18–110 J energy. A macro-homogeneous finite element model for the prediction of their response is implemented, considering the non-linear material behavior and intralaminar and interlaminar failure modes for the prediction of impact damage. The model accurately predicted the permanent indentation caused by impact. By applying the Ramberg-Osgood formulation, different initial stiffness values are examined to assess the post-impact unloading response. This approach reveals the significant role of initial stiffness in inelastic strain accumulation and its consequent effect on permanent indentation depth. A higher initial stiffness correlates with increased inelastic strain, influencing the impactor rebound and resulting in greater permanent indentation. By accurately predicting permanent indentation, and damage accumulation for different impact energies, this study contributes to a better understanding of the impact behavior of composite materials, thereby promoting their wider application.

On the optical wave structures to the fractional nonlinear integrable coupled Kuralay equation

This paper is mainly concerning the study of truncated M-fractional Kuralay equations that have applications in numerous fields, including nonlinear optics, ferromagnetic materials, signal processing, engineering fields and optical fibers. Due to its ability to clarify a wide range of sophisticated physical phenomena and reveal more dynamic structures of localized wave solutions, the Kuralay equation has captured a lot of attention in the research field. The newly designed integration methods, known as the modified Sardar subequation method and enhanced modified extended tanh expansion method are used as solving tools to validate the solutions. The goal of this study is to extract several kinds of optical solitons, such as mixed, dark, singular, bright-dark, bright, complex and combined solitons. Due to the many potential applications for superfast signal routing techniques and shorter light pulses in communications, the optical propagation of soliton in optical fibers is now a topic of significant interest. In nonlinear dispersive media, optical solitons are stretched electromagnetic waves that maintain their intensity due to a balance between the effects of dispersion and nonlinearity. In addition, exponential, periodic, hyperbolic solutions are generated. The applied approaches are efficient in explaining fractional nonlinear partial differential equations by providing pre-existing solutions and also producing new solutions by combining results from multiple processes. Additionally, we plot the contour, 2D, and 3D graphs with the associated parameter values to visualize the solutions. The results of this study show the effectiveness of the approaches adopted and help enhance comprehension of the nonlinear dynamical behavior of specific systems. We expect that a substantial amount of engineering model specialists will greatly benefit from our work. The findings demonstrate the efficacy, efficiency, and applicability of the computational method employed, particularly in dealing with intricate systems.

A non-ordinary state-based peridynamic model for creep–fatigue behavior and damage evolution

A peridynamic creep–fatigue model is proposed to study creep–fatigue mechanical responses and damage behaviors. A non-unified constitutive model is reformulated in a nonlocal form in the peridynamic-based framework. A probabilistic peridynamic damage criterion is proposed for characterizing creep–fatigue damage. The simulated mechanical responses are in good agreement with the results of creep–fatigue experiments conducted at high temperatures, which confirms the accuracy of the model. In addition, the damage evolution and morphology are well characterized by the model, and the damage mechanism is revealed. The model exhibits excellent potential for simulating nonlinear damage behaviors.

Fractional cyclic cohesive zone model for time-dependent fatigue behavior of soft adhesives under mode-II loading

Soft adhesives exhibit nonlinear viscoelastic behavior during cyclic loading, suggesting that their cycle-dependent fatigue behavior can be significantly affected by the time-dependent deformation behavior. Soft adhesives are frequently subject to various cyclic conditions in practical applications, presenting potential safety risks. This paper has proposed a fractional cyclic cohesive zone model (CZM) to characterize the time-dependent fatigue behavior of soft adhesives. To capture the nonlinear evolution of fatigue damage under asymmetric stress-controlled cyclic loading, a fatigue damage model that considers the contribution of in-situ stress/strain was incorporated into fractional-order viscoelastic model. The proposed CZM was validated through single-lap shear creep tests at various stress levels and fatigue tests at various stress amplitudes and loading periods. Furthermore, the impacts of stress ratio and peak stress level on fatigue failure under different loading periods were investigated using the proposed CZM. The results indicate that under a short loading period, the failure of the soft adhesives is primarily influenced by cycle-dependent fatigue damage, while under a long loading period, it is primarily affected by time-dependent creep deformation. Overall, this work offers a numerical strategy to describe the fatigue failure of nonlinear viscoelastic soft adhesives and to understand their time-dependent fatigue failure mechanism, with implications for product design and optimization.

A Novel Design and Analysis Adaptive Hybrid ANFIS MPPT Controller for PEMFC-Fed EV Systems

Now, the present electric vehicle industry is focusing on the fuel cell technology because its features are high flexibility, continuous power supply, less atmospheric pollution, fast startup, and rapid response. However, the fuel cell gives nonlinear power versus current characteristics. Due to this nonlinear behavior, the maximum power extraction from the fuel stack is quite difficult. So, in this work, an adaptive genetic algorithm with an adaptive neuro-fuzzy inference system (ACS with ANFIS) MPPT controller is introduced for finding the MPP of the fuel stack system thereby extracting the peak power from the fuel stack. The proposed hybrid maximum power point tracking (MPPT) controller is compared with the other MPPT controllers which are enhanced incremental conductance-fuzzy logic controller (EIC with FLC), improved hill climb with fuzzy logic controller (IHC with FLC), adaptive beta with FLC, enhanced differential evolutionary with FLC (EDE with FLC), and marine predators optimization with FLC (MPO with FLC). Here, these hybrid controllers’ comprehensive investigations have been carried out in terms of tracking speed of the MPP, oscillations across the MPP, settling time of the converter voltage, maximum power extraction from the fuel stack, and working efficiency of the MPPT controller. The fuel stack generates a very low output voltage which is improved by using the boost DC-DC converter, and the overall fuel stack-fed boost converter system is designed by utilizing the MATLAB/Simulink tool. From the simulation results, the AGA with ANFIS MPPT controller gives high MPP tracking efficiency when compared to the other hybrid controller.

Heterogeneity characterization of commercial structural papers

Abstract Evaluation of physical and mechanical heterogeneity in commercial paperboards is needed to promote their use in structural applications, especially within the field of packaging. Understanding the range of their behaviors is needed to compete with other materials in the current marketplace and expand in others. This work describes the physical and stiffness heterogeneities of twelve commercial materials using tensile tests in the cross-machine direction and several inverse analyses. The effects of grammage, thickness, and apparent density on tensile stiffness were evaluated in both the linear elastic and nonlinear regimes. Thickness and density provided the best explanation for elastic heterogeneous behavior in most of the materials; local grammage was not the best descriptor for any material. The analyses used here were not able to provide a good explanation of the nonlinear behavior, which was attributed to the development of large shear strains within the materials as they neared failure. This work provides a methodology for additional heterogeneous behavior examinations.

Modelling antecedent soil hydrological conditions to improve the prediction of landslide susceptibility in typhoon-prone regions

Most regional landslide susceptibility models do not consider the evolving soil hydrological conditions leading up to a multiple occurrence regional landslide event. This results in inaccurate predictions due to the non-linear behaviour of the terrain. To address this, we have developed a simple and efficient model that incorporates the mid-term evolution of soil hydrological conditions. The model combines a water balance model and a geotechnical model based on infinite slope theory. The analysis of 561 high-intensity rainfall events in a typhoon-prone region of the Philippines revealed that the percolation of water during the 5-month wet season is crucial in determining landslide susceptibility. Consequently, high-intensity rainfall events at the start of the wet season are less likely to trigger landslides, while later events are more hazardous. We analysed the change in landslide susceptibility during the 2018 rainy season by comparing the probability of failure (PoF) before and after three high-intensity rainfall events (July, August and September). Only the event in September caused a significant increase in the probability of failure (PoF). The model showed an accuracy of 0.63, with stable cells better represented than unstable cells. The antecedent hydrological conditions on the lower soil layers are responsible for changes in landslide susceptibility. Our findings support the hypothesis that new approaches to developing hydro-meteorological thresholds for landslide early warning systems should be evaluated, especially in regions with strong seasonality.

Humanoid Head Camera Stabilization Using a Soft Robotic Neck and a Robust Fractional Order Controller.

In this paper, a new approach for head camera stabilization of a humanoid robot head is proposed, based on a bio-inspired soft neck. During walking, the sensors located on the humanoid's head (cameras or inertial measurement units) show disturbances caused by the torso inclination changes inherent to this process. This is currently solved by a software correction of the measurement, or by a mechanical correction by motion cancellation. Instead, we propose a novel mechanical correction, based on strategies observed in different animals, by means of a soft neck, which is used to provide more natural and compliant head movements. Since the neck presents a complex kinematic model and nonlinear behavior due to its soft nature, the approach requires a robust control solution. Two different control approaches are addressed: a classical PID controller and a fractional order controller. For the validation of the control approaches, an extensive set of experiments is performed, including real movements of the humanoid, different head loading conditions or transient disturbances. The results show the superiority of the fractional order control approach, which provides higher robustness and performance.

Hybrid self-centering braces with NiTi-SMA U-shaped and frequency-dependent viscoelastic dampers for structural and nonstructural damage control

This study proposes a novel hybrid self-centering brace (HSB) with structural and nonstructural damage-control capabilities for the seismic resilience of building structures. NiTi-based shape memory alloy (SMA) U-shaped dampers and frequency-dependent viscoelastic dampers are included in HSBs to provide self-centering capacity for avoiding structural damage and velocity-proportional damping for nonstructural damage control, respectively. This study includes two major parts, i.e. component-level mechanical behaviour and system-level dynamic response evaluation of HSBs. The working principle and desired nonlinear behaviour of the HSB were first presented. Then, the preliminary design procedures were developed. After validating the efficiency of the modelling of SMA U-shaped and viscoelastic dampers using prior test results, comprehensive 3D finite element model simulations were performed to study the hysteretic responses of HSBs under cyclic loadings, where the influences of loading frequency, loading amplitude and viscoelastic damper’s contribution were considered. Analysis results demonstrated that the designed HSB can attain the desired deformation mechanism and nonlinear hysteretic behaviour during dynamic cyclic loadings. Higher loading frequency and amplitude and more contributions of the viscoelastic damper can introduce higher loading and energy-dissipation capacity. Subsequent dynamic analyses of the single-degree-of-freedom systems were conducted to assess the dynamic performance and advantages of HSBs. Results showed that compared with traditional self-centering systems without velocity-proportional damping, the systems with HSBs can achieve zero residual deformations, lower base shear demands and smaller absolute acceleration responses, confirming the promising potential of HSBs in developing seismic resilient building structures by reducing structural and nonstructural damage.

A Constitutive Model for Stud Connection in Composite Structures

The complexity of finite element analysis for composite structures can be significantly reduced by representing the connector and adjacent concrete as a macroscopic element. Nevertheless, the prevailing macroscopic models for shear connections predominantly employ nonlinear elastic theory. This approach introduces inaccuracies in estimating structural stiffness and load-bearing capabilities, primarily due to its inability to precisely capture the cumulative effects of plastic damage. In response, this study introduces a novel macroscopic elastoplastic model grounded in plasticity theory, aimed at accurately characterizing the nonlinear behavior of stud connections subjected to concurrent shear and tensile forces. This paper meticulously delineates the implementation of the elastoplastic constitutive model using the backward Euler method for numerical integration. It further articulates the derivation of the consistent tangent stiffness, which aligns with the convergence efficiency of the Newton–Raphson iterative approach. The computation of the element stiffness matrix for a two-node element is executed via the governing equation inherent to the finite element method. An exemplar macroelement test conducted in ABAQUS affirms the implicit backward Euler scheme’s stability and consistency across varying tolerances. Validation of the elastoplastic model against empirical test outcomes corroborates its efficacy, demonstrating the model’s precision in predicting the load–displacement behavior of stud connections under the influence of shear and tensile forces.

An efficient model for 3D analysis of steel frames exposed to fire

The paper presents a nonlinear concentrated plasticity frame element for advanced analysis of steel frames exposed to elevated temperatures. The element extends the formulation based on the generalized plasticity material model that was successfully applied to the analysis of steel and composite structures. It considers the material's nonlinear behavior, temperature-induced loading, strength and stiffness degradation typical for structures under fire conditions. The nonlinear geometry is taken into account with the corotational formulation. Because of the generalized plasticity relations adoption, the element can describe the gradual yielding of cross sections. At the same time, the implemented return mapping algorithm ensures the element's high computational efficiency. The governing element equations, selection of parameters and computer implementation are discussed in the paper, followed by element validation through the number of experimental data examples and other numerical models. The comparative analysis demonstrated the element's versatility and capability to accurately predict the structural response of steel frame structures exposed to fire.